A new SARS-like virus recently found in humans is "a threat to the entire world," according to the director-general of the United Nations' World Health Organization.

The so-called novel coronavirus "is not a problem that any single affected country can keep to itself or manage all by itself," Margaret Chan said Monday in her closing remarks at the 66th World Assembly in Geneva, Switzerland.

The world needs to pull together its resources to properly tackle the virus which, Chan said, is her "greatest concern" at present.

"We understand too little about this virus when viewed against the magnitude of its potential threat," she said, and more information is needed "quickly" and "urgently."

"We do not know where the virus hides in nature. We do not know how people are getting infected. Until we answer these questions, we are empty-handed when it comes to prevention. These are alarm bells. And we must respond," she said.

Novel coronavirus is part of a family called coronaviruses, which cause illnesses ranging from the common cold to SARS, or Severe Acute Respiratory Syndrome, as well as a variety of animal diseases. However, the new virus is not SARS.

Novel coronavirus acts like a cold virus and attacks the respiratory system, the Centers for Disease Control and Prevention has said. But symptoms, which include fever and a cough, are severe and can lead to pneumonia and kidney failure. Gastrointestinal symptoms such as diarrhea have also been seen, according to the WHO.

It's not yet known how humans contract the virus, experts have said. Most of the cases so far have been seen in older men with other medical conditions; precise numbers are hard to come by, as officials don't know how many people might contract a mild form.

Cases have been identified in eight countries including France and Saudi Arabia, according to the WHO. Other European countries include Germany and the United Kingdom.